The principal who was slugged in the face by a music-blasting student penned a heart-felt letter to his other students on the Murry Bergtraum High campus, telling them he’ll be back as soon as possible.

“As many of you know, I was injured yesterday during an incident in school,” said Dr. Matthew Tossman in the letter addressed to kids at Manhattan Early College School for Advertising, one of four schools on the Lower Manhattan campus.

“I am writing to thank you for the outpouring of support that I received from this community; your phone calls, emails, and kind words have lifted my spirits.”

Tossman added he was recovering at home and “will be back at school as soon as I am able.”

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The principal was beaten Monday by an 18-year-old student, whose lawyer said is acting out because his mother died of a brain aneurysm in his arms last year.

The student, Luis Penzo – who was arraigned on charges of second degree assault and held on $5,000 bail – was in the hallway blasting music from his headphones when Tossman asked him to turn it down.

Penzo not only refused, police say he cold-cocked the administrator and continued to punch him after he was down.

Students at the troubled business-themed campus – which houses four different schools – complained the place was out of control.

“They should just shut the school down,” said Dashawn Reid, 15.

She pointed to an arrest on Oct. 7 of a student who came to school stinking of weed and carrying a gun in his backpack.